X^, Y^ solves this problem.

X和Y解决了这个问题
So if this thing really makes him better off than what he chose,

因此如果这比他所选择的更能改善其境况
it can't be that it was affordable

这将是他所不能负担的
-otherwise he would have bought this instead.

否则他会取而代之购买此组合
So it has to be that for I,

因此I不得不选择此组合
this bundle cost more than he can afford.

因为他无法承担过高成本
That's why he didn't choose it.

这就是为何他没有选择此组合
So this relies on agent rationality.

这取决于主体理性
Everybody given his choices,

每个人做出自己的选择
he doesn't care about the rest of the world,

他并不关心其他人的选择
but given his choice everybody's doing the best thing he can.

而只是做出能够使其利益最大化其的选择
Shiller would say, "People make mistakes.

Shiller会说大家都在犯错误